Cyclic-Frequency Shift OFDM for Multipath Resistance
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Solution Overview
Problem
Conventional spread spectrum technologies, such as DSSS, FHSS, and CSS, face challenges including poor multipath resistance, high power consumption, difficult synchronization, reduced bandwidth usage, and slower transmission rates, particularly in environments with low signal-to-noise ratios.
Innovation Solution
The CFS-OFDM spread spectrum technology employs cyclic-frequency shift and orthogonal frequency division multiplexing to convert bits into frequency domain symbols, utilizing frequency reordering and Gray code encoding to enhance stability and transmission efficiency, even under low signal-to-noise conditions, by forming cyclic frequency shifts that correspond to different bit values and incorporating a cyclic prefix to improve multipath immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DSSS spread spectrum technology is used to achieve broadband transmission, then transmission stability is improved, but power consumption increases due to high-speed transmission
Solution Approach 1:
The patent divides the broadband signal into multiple orthogonal frequency subcarriers, each carrying a portion of the data. This segmentation allows the system to achieve spread spectrum benefits without requiring extremely high-speed single-carrier transmission, thereby reducing power consumption while maintaining transmission stability through the combined effect of multiple subcarriers.
Solution Approach 2:
The patent introduces cyclic frequency shifting that dynamically changes the frequency positions of subcarriers between transmissions. This dynamic frequency allocation provides frequency diversity, improving transmission stability under varying channel conditions while allowing flexible resource utilization that optimizes power efficiency.
2Adaptability or versatility
If FHSS spread spectrum technology is used to divide bandwidth into sub-bands, then frequency diversity is achieved, but synchronization difficulty increases and transmission rate decreases
Solution Approach 1:
The patent maintains orthogonal relationships among all subcarriers throughout the frequency domain, ensuring that each subcarrier operates at an equivalent spectral efficiency level. This orthogonal structure simplifies synchronization compared to FHSS, as the receiver can efficiently correlate with the known orthogonal patterns without complex frequency hopping synchronization requirements.
Solution Approach 2:
The patent employs periodic cyclic frequency shifting patterns that repeat at regular intervals. This periodic structure provides inherent synchronization references, making it easier for the receiver to lock onto the transmitted signal and maintain synchronization, thereby reducing the complexity associated with frequency diversity implementation.
3Temperature
If CSS spread spectrum technology is used to transmit each bit with a chirp signal, then broadband transmission is achieved, but transmission rate decreases because each chirp carries only one bit
Solution Approach 1:
The patent segments the data stream into multiple parallel channels, with each orthogonal subcarrier carrying independent data symbols. This allows multiple bits to be transmitted simultaneously across different frequency subcarriers, dramatically increasing transmission rate while maintaining broadband characteristics through the collective bandwidth of all subcarriers.
Solution Approach 2:
The patent combines multiple orthogonal frequency subcarriers into a single transmitted signal, where each subcarrier contributes to the overall broadband transmission capability. This merging of parallel frequency channels achieves both high transmission rate (through parallel data transmission) and broadband coverage (through the aggregate frequency range of all subcarriers).
Data Source
AI summary
The invention discloses a cyclic-Frequency shift orthogonal frequency division multiplex spread spectrum device, comprising: at least one communication device for performing the conversion between a series of bits and a frequency domain symbol out of a plurality of frequency combination patterns; wherein different patterns correspond to different bit values; and the device forms a cyclic frequency shift value utilizing a frequency reordering, each of the cyclic frequency shift values corresponding to a frequency combination pattern.